The specific rate constant, k, for radioactive beryllium–11 is 0.049 s–1. What mass of a 0.500 mg sample of beryllium–11 remains after 28 seconds? This reaction was found to be first order.

The mass of sample that remained is 0.127 mg

Explanation:

The integrated rate law equation for first-order kinetics:

......(1)

Given values:

a = initial concentration of reactant = 0.500 mg

a - x = concentration of reactant left after time 't' = ?mg

t = time period = 28 s

k = rate constant =

Putting values in equation 1:

Hence, the mass of sample that remained is 0.127 mg

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